Railway-traffic-controlling apparatus



Aug. 19, 1930. P. N. BossART RAILWAY TRAFFIC CONTROLLING- APPARATUS Filed Feb. 7, 1927 |NVENTOR. F./V.Bo5.s4r

Patented Aug; 1930 f UNITED sr T-as ATE T- orries ZPAUL N. BOSSART, or SWISSVALE, PENNSYLVANIA, AssIeNon To run UN oN swrrcn & sIoNAL COMPANY, or SWISSVALE, PENNSYLVANIA, A coaronA'r ON OF PENNSYLVANIA RAILwAY-TRAFFIC-GONTROLLING AIPLBAT'UB Application illed'Februai-y 7, 1927. Serial No. 166,407.

. My invention relates to railwa traflic controlling apparatus, and particu arly to apparatus the type comprising mean's for supplying the trackway with alternating currentwhich is periodically varied at different frequencies, and governing means on the train selectively responsive to the frequency of such variations. .I will describe one form of railway traffic controlling apparatus embodying my in- -vention, and will then point out the novel features thereof in claims; The accompanying drawing is a'diagra matic view illustrating one form of railway traflic controlling apparatus embodying my invention. Referring to the drawing,- the, reference characters 1 and 1 designate the track rails of a stretch of railway track over which traffic normally moves in the direction indicated by the arrow. These rails are divided, by means of insulated joints 2, into a plurality of successive track sections only one of which, I A-B, is shown complete in the drawing. Train controlling current is supplied to the rails ofthis section from-a suitable source of energy such asan alternator G. The current supplied to the trackway by this alternator may be of a fre uency of the'order of the usual commercia alternating current such for example as 60 cycles or 100- cycles per second. f p

The supply of current to the track rails is controlled by a coding device designated in general by the reference character X and comprising a plurality of rotatable cams each designated by the reference character C with a suitable distinguishing exponent. The cams C are driven at a constant speed-by a suitable motor M which is supplied with current from the alternator G. The cam'C is provided with a plurality of swells 8- spaced about its perip cry and which swells successively engage a contact 3 to periodically close the contact as the cam'C is rotated. In similar manner the cams C and Ct are rovided with .different numbers of swell 8' which control contacts 4 and 5, respectively. One terminal of the alternator G is constantly connected with rail 1 of section A-B, and

frequency of; 180 cycles the other terminal of the alternator is conl nected with the rail 1 through one of the contacts3, 4'01? 5, depending upon trafiic con-.

ditions. It is manifest that the alternating current supplied to the rails of the trackway by alternator G is periodically varied at'the frequency of operation of the contact of the device X that is interposed between the alternator and the track'rail l, The coding device X may be constructed to cause such variations at an reasonable frequencies, but 1 for purposes'o illustration, I will assume that the cams C are rotating at 20 revolutions I per minute, that cam Chas 4 swells, that 'camC? has 6 swells, and that cam C has 9 swells. The selection between the several contacts'of the coding device X in accordance with traflic conditions may be accomplished 1 I poses it is sufiicient to state that home 'relay H is normally energized but is de-energized when a'train occu ies the section immediately to the right 0 point B. The distant relay L is also normally energized but is de-energizedwhen a train occupies either the first or'the second section immediately to the right of oint B. With the ap aratus thus far descri ed, when relays H an L are both energized so thatv front contact 6-6 of relay H and front contact 77 of relay'L are closed, current from alternator G, which current I will assume to be of 100 cycles per second, is supplied to the track' rails oyer contact 5 operated by cam C Under these conditions the alternating current supplied to the trackway is periodically varied at a er minute. Current supplied to the trac way under these conditions, I will hereinafter term the proceed code. When relay H is-energized and relay L is de-energized,'the closing of back contact 77 of rela L includes contact 4 controlled by cam 2 in the trackway circuit, and under these conditions the trackas v quency of 80 cycles er minute, which current I will call the s ow code.

The train indicated diagrammatically at V is provided with governing means which is responsive to the frequency of the periodic variations in the 100 cycle current supplied to the trackway. In the present embodiment of my invention the train is provided with two magnetizable cores 11 and 11 located in advance of the forward axle 10 and disposed in inductive relation to' the two track rails land I 1, respectively. Core 11 is provided with a winding 12, and core 11 is provided with a winding 12, the two windings 12 and 12 being connected in series'in such manner that the voltages induced therein by train controlling current flowing in opposite directions in the trackrails at any instant are additive. Windin s 12 and 12 are connected through an amp 1fier- 13 and a transformer Q, with a polarized relay B. When train controlling current is being supplied tothe .trackway, 'pulsatin' energy is delivered to the rimary of trans ormer Q at the frequency of the periodic variations in such trackway current. For each im ulse of energy supplied to transformer Q, uring the increase of such current, an impulse of onerelative polarity is supplied ta relay It and durin the decrease of such current, an im ulse o the opposite relative polarity is supp ied to the relay. The

rela R is responsive to the relative polarity of t e current supplied thereto and it follows that when the train'controlling current supplied to the trackway is bein periodically varied, the relay R is operated to close its normal and reverse contacts 1515 and 15-.15 alternately at a frequency which corresponds to the frequency of the variations of the trackway current.

Associated with relay R is a transformer T comprising a primary 16 and a secondary 17. Direct current is supplied to the primary 16 of transformer T from a suitable source of energy such as a battery D and the supply of in the t-rackway current.

ated intermittently, the current in primary 16 of transformer T is periodically reversed and re-established in ori inal direction at the same frequency as t e periodic variations As a result of this periodic current in'the primary of transformer T there is induced in. the secondary 17 .an alternating lectromotive force of a corresponding frequency, which electromotive force is applied to a plurality of circuits each designated by thereference character F with a distinguishing exponent, and each comprising a reactor 18 and a condenser 19 by means of which the several circui s are tuned respectively to the frequencies of the variations in-the train con trolling current; For example circuit F is tuned to resonance at the frequency of the interruptions in the proceed code or 180 cycles per minute. A relay K is connected across a portion of reactor 18 of circuit F throu h a rectifier J". In similar manner circuit 2 is tuned to resonance at 120 cycles per minute and relay K is connected across a portion of reactor 18 of this circuit through a rectifier J Relay K is connected, through rectifier J with a portion of reactor 18 of circuit F which circuit is resonant at cycles per minute.' The rectifiers J may be of any suitable type but I have discovered that the operation of the apparatus is materially improved if the rectifiers are of the type comprisin a symmetrical conductors each made up 0 a metallic member having formed thereon a compound of the metal. Rectifiers of this type 6 are shown and described in an application for Letters Patent of the United States Serial No. 1111, filed January 7, 1925, by Lars O. Grondahl, for uni-directional current carrying devices. I have discovered that rectifiers 5 of this type which exhibit the peculiarity of material y increasing their rectifying ratios in response to increases in the electromotive force applied thereto may be used to greatly increase the selectivity of a filtering cir- 'cuit. The advantage obtained by rectifiers of this type in the apparatus illustrated will be explained in detail hereinafter.

In explaining the operation of the appa-- ratus as a whole, I will first assume that the proceed code is'being supplied to the trackway so that the trackway current is being interrupted at a fre uency of 180 cycles per minute. Relay R t erefore operates at a rate of 180 cycles per minute and alternating 2 current of a corresponding frequency is sup.- plied to each of the circuits F. At this frequency circuits F and F are detuned so that the electromotive force across those portions of reactors 18 of these circuits to which the corresponding relays K are connected is comparatively small. Circuit-F is tuned to resonance at this frequency and the resonant rise of electromotive force in reactor 18 is comparatively large. A'compar'atively large 13o a s electromotive force is therefore applied to rectifier J resulting in acomparatively large current in the relay K. 'Due to the increase in electromotive force applied to the rectifier J a the rectifying ratio 6f this device also increases. It follows that a correspondingly increased proportion of the current is supplied to relay K". As a resultof the commation of the tuned circuit'and the rectifier,

the sensitivity of .the relay K to the frequency of the current supplied by secondary 17 of transformer T is materially im 'roved, and although relay K is adjusted to ecome energized when the proceed code is being supplied tothe trackway a very small variation in the frequency of the current supplied to the filter circuits will so reduce the-current in the relay K that this relay will open. When the train is receiving the prbceed code,

therefore, relay K is energized, but relays K and K are de-energized. ,Under these conditions, current from battery D flows through front contact 24-24 of relay'K to light lamp 20, thereby displaying a proceed indication. I

I will now assume that the caution code is being supplied-to the trackway so that 1 cycles per second. Alternatin current of a" relay R is operating at a frequency of 120 corresponding frequency is t erefore supplied to the circuits F by secondary 17 of is "a comparatively transformer T. Under these conditions the current supplied to relays K and K isnot suflicient to energize the relays but due to the tuning efiect. of circuit F which filter isresonant at 120 cycles per minute, there high resonant electromotive force in reactor 18. ,As a result the rectifying ratio of J 2 is comparatively'high and and K are both de-energized, but circuit F is tuned-to resonance at the frequency of the current now supplied by secondary 17 of transformerT so that relay K is energized and current from battery D flows over back contact 24=-24" of relay K, back contact 25-25 of relay K and front contact 2626 ofrelay K to lamp 22. Lamp 22 is therefore lighted to indicate slow.

.If section A-B were occu ied by a second train located between train V and-'point B, train controlling current would be shunted away from train .V by the wheels and axles of such second train. As a result relay R would be continuously de-energized. If, for this reason, or for any other reason, relay B. should fail to operate intermittently, the supply of energy to all the relays K would be discontinued and these relays would .be open. Current would then flow from battery D, over back contact 24-24 of relay K back contact.25-25 of relay K and back contact 2626 of'relay K to lamp 23, thereby light.-

ing this lamp to display a stop indication.

tifier connected in this manner iselectrically equiyalentto a small resistance connected in series with the reactor, and when the resistance of the rectifier increases, as it does when the power in the tuned circuit decreases, it has the same. effect as a decrease in the equiv alent series resistance. The net result isthat the rectifier power output, that is, the relay current, is decreased. This operation assists materially in producing sharp selectivity between frequencies supplied to the apparatus.

Theresonant circuits F are tuned to frequencies of a comparatively low order of magnitude and I ave discovered that in order to accomplish sharp tuning under these conditions it is desirable 'to construct each reactor 18 with a magnetizable core 18 and to so proportion the parts of the reactor that at the maximum flux density of the core, the iron-comprising the core exhibits approximately its maximum permeability. This maximum'flux density of the core will, of course, be variable if the electromotive force of source D is variable, as would be the case if the source were the usual headlight generatoron the locomotive. In such event,it

is obvious that the parts should be so proportioned that the maximum permeability of the core of each reactor, and hence the maximum inductance of each reactor, will correspond substantially to the maximum flux density for the lowest. value of current for which the associated relay K is intended to operate.

Wherever, therefore, in the specification and claims, I have used in this connection, the core of each reactor, and hence the maxmum value of the current or similar expressions, it is understood that I mean the peak values of the flux density or current for the minimum operating current, when the electromotive force of'source D is variable. One advantage of this construction is that the inductive reactance of a reactorof the type described decreases in response to reductions in the current supplied thereto. It follows that any decrease 1n the current through one of the reactors 18 due, for example, to the response of the tuned circuit E including such reactor, to .current'of a frequency di erent from that to which the circuit is tuned, decreases the inductive reactance of such reactor and causes the associated circuit F to be tuned to resonance at a slightlylhigher fro-1 quency than that to which it is normally tuned.

possible to accomplish sharper tuning than with a simple tuned circuit and this tuning is substantially unaffected by variations in the wave form of the current supplied by transformer T. One advantage of this feature is that the apparatus may be operated successfully by the output produced by simply making and breaking a circuit. It will be apparent that the modulations inthe current supplied to primary 16 of transformer- T are practically square, but the harmonics are choked out and the apparatus gives substantially the same response as if the primary currents were modulated according to a pure s ne wave.

I havedisclosed apparatus which supplies only three codes to the, track'wayand have shown train carried governing means adapted to distinguish only between these three codes.

It should be understood, however, that my invention is not limited to this number of codes but that the equipment could be expanded to provide additional code frequencies and additional tuned circuits on the train to select between such frequencies.

'Although I have herein shown and described only one form of railway traific controlling apparatus embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my inventio Having thus described my invention, what I claim is:

1. In combination, a source of alternating currents of different frequencies of the order of 80 to 180 cycles per minute, a plurality of circuits all receiving energy from the source and each comprising a reactor and a condenser tuned to resonance at one of said frequencies, a relay connected with a portion of each reactor, and a rectifier interposed between each relay and the associated reactor.

-2. Railway trafiic controlling apparatus comprising means for supplying alternating current to the trackway, means for eriodically varying such current at different frequencies, a' train carried relay responsive nected with a to such variations but not to such alternating current, a transformer, means controlled by the relay for supplying periodic currents to the primary of the transformer at a frequency depending. upon the frequency of such variations, a plurality of parallel circuits connected with the secondary of the transformer and each tuned to resonance at a' diflerent one of said frequencies, a plurality of other relays, one for each of said circuits, and each connected inp'arallel with a portion of the associated circuit, and governing means selectively controlled by the other relays. v

3. Railway traific controlling apparatus comprising means for supplying alternating current to the trackway, means for pcriodically varying such current at diiferent frequencies, a train carried transformer, means for supplying periodically varying current to the primary of the transformer at the same frequency as the frequency of such variations, a plurality of parallel circuits connected with the secondary of the transformer and each tuned tores'onance at a different one of said frequencies, a'plurality of other relays, one for each of said circuits, and each connected in parallel with a portion of the associated circuit, and governing means selectively controlled by the other relays.

4. In combination, a source of periodic current, a reactor comprising'a winding connected with the source and a magnetizable core offering its maximum permeability to the flux created therein by maximum Values of the current in said winding, means for tuning the winding to resonance at the frequency of such current, and a relay connected with a portion of the winding.

5. In combination, a source of periodic currents of difierent frequencies, a plurality of reactors each comprising a winding connected with the source and a magnetizable core so proportioned that the maximum dens ity of the flux created in the core by current supplied to the winding from the source approximately corresponds to the maximum permeability of the core, means for tuning each reactor to resonance at one ofsuch frequencies, and a plurality of" relays one conportion of each said reactor winding.

6. Railway traflic controlling apparatus comprising means for supplying the trackway with alternating current periodically varied at diiferent frequencies, a train carried reactor comprising amagnetizable core and a winding receiving energy according to such variations and tuned to resonance at one of such frequencies, said core having its maximum permeability at substantially the density of the flux createdtherein by maximum values of the current supplied to the windings, a relay connected across a portion of the winding, and governing means controlled by the relay.

, 7. Railway traflic controlling apparatus comprising means for supplying the track rails with alternatin current of a commercialfrequency perio ically varied atdifferent frequencies of the order of 80 to 180 cycles per'minute, a train carried relay controlled bysaid current-and respondin to the periodic variations thereof, a trans ormer, means controlled by said rela for supplying the primary of said trans ormer with current atthe frequency of operation of the relay, a

' plurality of parallel circuits connected with the secondary of said transformer and tuned to resonance respectively at the several frequencie'sof periodic variation of .said track rail current, each circuit including a reactor comprising a winding on a magnetizable core which ofiers its maximum permeability to the flux created therein by the maximum value of the current in the associated winding, a fullwave rectifier connected across a portion of each reac or andhaving the characteristic of increasing its rectifying ratio with 'increases of voltage, a relay supplied with current by each rectifier, and governing means controlled b said latter relays.

8. Railway tra c controlling apparatus comprising means for supplying the track rails with alternatin current of a commercial frequency perio ically varied at diiferent frequencies of the order of 80 to 180 cycles per minute, a train-carried relay con trolled by said current and responding to the periodic variations thereof, a plurality of circuits tuned to resonance respectively at the several frequencies of periodic variation of the current in the track rails, means for supplying all said circuits with periodic current at the frequency of operation of the relay, a

' rectifier connected across a portion of each rails with alternatin cial frequency perio 'cally varied at difiersupplying. all said circuits with periodic cur-- rent at the frequency of operation of the relay, a full wave rectifier connected across a -portion of each reactor and havin the characteristic of increasing its' recti g rat o 7 with-increases of voltage, a relay supplied with current by each rectifier, and governing means controlledfllg said latter relays. i -10.- Railway tr c controlling apparatus the track comprising means for supplying rails with alte'rnatin current 0 a commercial frequency perio 'cally varied at difiertent frequencies of the order of 80 to:180 cycles per minute, a train carried relay controlled by said" current and responding to the periodic variations thereof, a plurality of circuits tuned to resonance respectively-at the several frequencies of'periodic variation of the current in the track rails, each circuit including a reactor comprising a winding on a magnetizable core which, ofiers its maxi- .a mum permeability to the flux created therein by the maximum value of the current in the associated winding, means for supplying all said circuits with periodic current at ,the

frequency of operation of the relay, a rectifierconnectedacross a portion of each reactor, a relay'supplied with current by each rectifier and governing means controlledby said latter. relays.

'- 11. In combination, a source of periodic current, a reactor comprising a winding connected with sald source, ineans for tuning said winding to resonance at the frequency of said current, a full wave rectifierconnected across a portion of said winding and having the characteristic of increasing its rectifying ratio with increases in voltage, and an electro-responsive, device supplied with current by said rectifier.

12. Railway trafiic controlling apparatus comprising means for supplying the track'-' way with alternating current, means for periodically varying such current at different frequencies, and alplurality of train carried devices all controlled'by energy received from the trackway and respectively tuned .to electrical resonance at said frequencies.

13. Railwaytraflic controlling apparatus comprising means for supplying the track way with alternating current periodically varied at different frequencies, aplurality of devices on the train respectively tuned to electrical resonance at such frequencies, and means for supplyin each such device with periodic current of t e same-frequency as the.

variations of the first named current. v

14. Railway trafiiccontrolling apparatus comprising a train carried transformer, means located partly in the trackway for supplying the primary of the transformer with periodic. currents of different frequencie'sof the order of 80 t9 180 cycles per minute, and a plurality of devices c'onnectedwith the such frequencies. p 7

- 15. In combination, a source of alternating current, means for periodically varying the current delivered by the source at difierent frequencies, a plurality of devices receiving energy according to such variations and tuned respectively to electrical resonance at such 20 Secondary of the transformerthrough circuits tuned respectively to electrical resonance at the track I frequencies, and governing means selectively controlled by such devices.

16. Railway trafiic controlling apparatus comprising means for supplying the trackway with alternating current, means for periodically varying such current at difierentfrequencies, a plurality of rectifiers on the train, a plurality of relays one connected inthe output circuit of each rectifier, and an input circuit for each rectifier receiving alternating current of the. same frequencies as the frequencies of such-variations and tuned to resonance at such frequencies respectively.

- 17. Railway traflic controlling apparatus comprising means for supplying the trackway with alternating current periodically varied at diiferent frequencies, a first train carried relay controlled by energy received from the trackway and operating at the fre quency of such variations, two other relays on the train, means controlled by the first relay for supplying such other relays with peri- 'odic current of the frequency of such variations, means for tuning one of such other relays to electrical resonance at one of such frequencies, and governing means selectively controlled by such two other relays.

-18. Railway traflic controlling apparatus comprising means for supplying the trackway with alternating current of commercial frequency periodically'interrupted at different frequencies of the order of 80 to 180 cycles per minute, and a plurality of train carried devices all controlled from the trackway and tuned respectively to electrical resonance at the different frequencies of periodic interruption of said trackwa current.

19. Railway traffic controlling apparatus comprising means for supplying alternating current to the trackway, means for eriodical- 'ly varying such current at di erent fre-- ing such current, means for producing a second alternating current the frequency of which depends uponthe frequency of the variations of the current from the first source,

and a plurality of devices each tuned to resonance at a different frequency andall receiving such second alternating current. 21. In combination, a section of railway track, means for supplying the track rails 'ofsaid stretch with alternating current periodically varied at different frequencies, and a pllurality of governing devices all contro ed by energy received from the track rails and respectively tuned to electrical resonance at said frequencies.

22. Railway'traflic controlling apparatus comprising means for supplying the track- 'Way with alternating current periodically difierent frequencies, and a pluralvaried at ity of governing devices all controlled by energy received from the trackway and respectively tuned to electrical resonance at said frequencies.

23. Railway traflic controlling apparatus comprising means for supplying the trackway with alternatingzcurrent periodically varied at different frequencies, a plurality of devices all controlled by energy received .from the trackway and respectively tuned to electrical resonance at said frequencies, and governing means selectively controlled by said devices.

24. Railway traflic controlling devices comprising meansfor supplying the trackway with alternating current periodically varied at different frequencies in accordance with traflic conditions, a plurality of devices controlled by energy received from the trackway and respectively tuned to electrical resoname at said frequencies, and governing means selectively controlled by said devices.

25. In combination, a source of alternating current periodically varied at different frequencies, a plurality of devices-rece ving energy in accordance with such varlations and tuned respectively to electrical resonance at suchfrequencies, and governing means se- 1 lectively controlled by suchdevices.

26. In combination, a source of varying current of one periodicity, means-for periodically varying the current delivered by such source at a selected one of a plurality of different frequencies, a plurality of devices all. controlled by energy-from said source .nd each tuned to electrical resonance at an individual one of such different fre-' quencies, and governing means selectively controlled by said devices.

27. In combination, a source of periodic current", meansv for periodically varyingthe current delivered by said source at difierent" frequencies, a plurality of devices receivlng' energy according to such variations .and tuned respectively'to electrical resonance at such frequencies, and governing means selectively controlled by said devices.

28. In combination, a source of periodic current, means for periodically varying the current delivered by said source at different frequencies of the order of 80 to 180 cycles per minute, a plurality of devices all controlled by energy receivedfrom said source andtuned respectively to electrical resonance at. such frequencies, and governing means selectively controlled by said devices.

29. Railway trafliccontrolling apparatus comprising means for supplying the trackway with periodic current periodically intertrical'resonance at'the different frequencies of periodic variations of said trackway current. Y

30. Railway traific. controlling apparatus comprising means for supplying the tracks way Withalternating current of commercial frequencies periodically varied at different frequencies of theorder of 80 to 180 cycles per minute, and a plurality of governing devices all controlled from the trackway andtuned respectively to'electrical resonance at a the different frequencies of the periodic variations of said trackway current.

31 Railway traific controlling apparatus comprising means for supplying the track- Way with periodic current regularly varied at difierent frequencies, and a plurality of governin devices all controlled by energy received roin the trackway and respectively tuned to electrical resonance at said fre-f quencies.

32. In a frequency. selective circuit supplied with periodic current, a condenser,.and. an lron core reactor for tunlng said circuit to A 33. In a frequency selective circuit supplied with periodic current, a condenser, and

an iron core reactor for tuning said circuit to resonance at the frequency of such current,-

the core of such reactor exhibiting substan'. tially its-maximum permeability for the flux density corresponding to the peak values orthe resonant current in said circuit. 34. In a frequency selective circuit sup plied with periodic currents of difierent frequencies, a capacity and aniron core reactor for tuning said circuit to resonance at one of said frequencies, said reactor oifering "substantially its maximum inductance at current values corresponding to resonance in said cir-. cuit.

- 35. In combination withasource of peri- 53 quency of said current for. the specific value of current in said circuit corresponding to the resonant condition of the circuit, the inductance-of said reactor decreasing in res "onse "to any change insaid current from'sai s ecific value to detune' said circuit at said e quency.

36. In a plied with periodic current, a condenser, and 1 an iron core reactor for tuning said circuit to .4 resonance at the-frequency of such current,

,. 'odiccurrent and a load, a circuit for sgitpply' the coreand winding of such reactor being so proportioned that increases in current in said circuit up to the value corresponding to resonance increase the inductance of said-reactor.

37. In a frequency selective circuit sup- N plied with periodic currentsof different frequencies, a capacity and. an iron core reactor for tuning said circuit to resonance at one of said frequencies, said reactor having its core and winding so proportioned that any change in the magnitude of such current due to a change in the frequency of such current away from the resonant frequency of the circult decreases the inductance of said reactor and detunes the circuit at said one frequency. s 38. In combination, aisource of period c current, a circuit receiving energy fromv said source and containing a-condenser and a reactor for tuning said circuit to resonance at the frequency of such current, and a magnetizable core for said reactor having its maximum permeability corresponding substantially to the peak values of the current in said circuit at resonance, whereby any change in the current in said circuit from its resonant .90 value decreases the inductance of said reactor andtunes thecircuit to resonance at a higher frequency than that of said source.

39. In combination, a source of periodic current, a circuit receiving current from said source and including a reactor having a magnetizable core and a condenser the impedance of which balances the maximum impedance of said reactor at the frequenicy of saidsource, the reactor being so propo ioned that the maximum impedance of said reactor corresponds to the maximum values of the magnetization of said core. r

40. In combination, a source of periodic current, a circuit containing a condenser and a reactor having a winding for tuning said circuit to resonance at the frequency of] such current, a magnetizablecore forsaid reactor exhibitingfsubstantially its maximum permeability at the peak values of the current in said circuit'iat resonance, and a load c 'on-' nected with a portion of said winding.

41. In combination, a source of periodic current, acircuit'contaming a condenser and said circuit at resonance, a full waverectifier 120,

connected across a portion 0 said winding 7 and having the characteristic of mcreasmg its rectifying ratio with increases in the .electromotive force applied thereto, and an electrorespons'ive device supplied with current j y 1 by'said rectifier. frequency} selective circuit supa minute, a circuit receiving energy. from said source and containing a condenser and an iron core reactor having its maximum impedv ance equal to the impedance of said condenser atthe frequency of said source, and a relay receiving energy from said circuit.

43. In combination, va source of periodic current of the order of"80 to 180 cycles per minute,-a circuit receiving energy from said source'and containing a condenser and an iron core reactor having its maximum impedance equal to the impedance of said condenser at the frequency of said source,

'a rectifier connected across a portion ofsaid reactor and havin the characteristic of increasing its recti sponse to increases in the electromotive force supplied thereto, and a relay receiving energy from said rectifier.

&4. The methodof rendering a circuit sel .ective to the frequency of the current supplied thereto which consists in combining in the circuit a capacity and an iron core reactor tuned to resonance at a particular frequency,

and proportioning the parts-s0 that the inductance of said reactor decreases in response to a change in-the current in the-circuit from its resonant value".

45. 'The method of rendering'a relayselectively responsive to the frequency of the ourrent supplied thereto which consists of supplying current to the relay througha circuit containing a capacity and a reactor, and

proportioning the parts so that for the maximum inductance of the reactor the circuit is .resonantat a particular frequency.

' 46. The method of tuning a circuit to resonance at a particular frequency which consists in combining-in the circuit a capacity and a reactorhaving-a. variable inductance'the ma'ximum value of'which tunes said capacity to resonance at said frequency and corresponds to the peak values of theresonant I current in said circuit.

force a plied thereto. he'methodof discriminating between '47. The method. of. rendering a relay selectively responsive to the" frequency of the current from a source which consists in supplying the current to .a circuit including a capacity and a reactor having a variable ln- .ductance the maximum value of which tunes said capacity to resonance at a particular frequency and corresponds to the peak values lng ratio in 'reand governing meansmaximum values with the maximum values of the magnetlzation of such core.

49. In combmat1on, a source of per1od1c currents of different frequencies of the order 7 of 80 to 180 cycles per minute, a plurality of rectifiers, 'a relay connected with the output circuit of each rectifier and an input cir-. cuit for each. rectifier including the source,

a condenser, and a reactor in series and each such input circuit beingtuned to resonance at a different one of such frequencies,

50. Railway traflic controlling apparatus comprising means for supplying the trackway with alternating current periodically varied at different frequencies, two train carried relays, a circuit for each relay sup- 4 plied with periodic-current ofthe same frequency as such variations, means included in one, circuit for tuning such circuit to electrical resonance at oneof such frequencies, selectively. controlled bysadrelaysw 51. Railway traffic controlling apparatus. comprising means for-supplyingthe trackway with alternating current periodically train carried relays, a plurality of circuits each including one of said relays and tuned respectively to such-frequencies, means for supplying-all said circuits with periodic cur-' the variations in the trackway current, means included in one said circuit for tuning such circuit to resonance at 120 cycles per minute, and governing means selectively controlled by said relays. 1

In testimony whereof I aflix m signature.

of the resonant current in said circuit and connecting said r'elay'with-a portion of said reactor through a rectifier having the characteristic of increasing its rectifying ratio in response to'increa'ses in the electromotive periodic. currents of different frequencies whichfeonsists in supplying the currents to a circuit including a reactor having a magnetizable core and 'a condenser having the same impedance as themaximum impedance of said reactor at one of said frequencies, and

proportiom'ng said reactor'in such manner that the impedance of the reactor'reachcs its such current at 80 or 120 cyclesper minute according to traflic conditions, two relays on 'the train each provided with'a circuit receiving periodic current of the same frequency as 4 o0 varied at different frequencies, a plurallty of 

